This invention relates to an apparatus for removing foreign metal bodies from a travelling fiber mass which is advanced pneumatically in a conveyor duct in a spinning preparation plant. The duct has a branch-off location accommodating a deflector (channelling) mechanism for the foreign bodies and, upstream of the branch-off location--as viewed in the direction of fiber conveyance--a metal detector is arranged which is operatively coupled to the deflector mechanism in such a manner that the latter is moved into its deflecting (foreign body removing) position when a foreign metal body passes by the detector and is sensed thereby.
In a known apparatus of the above-outlined type there is provided a horizontal fiber conveying duct between two serially arranged fiber processing machines and the branch-off location as well as the metal detector are associated with the duct. The distance between the metal detector and the branch-off location of the duct is so designed that the time necessary for conveying the fiber tufts from the zone of the metal detector to the branch-off location is greater than the switching time needed for the deflecting mechanism. Because of the required reaction time, delay tracks between the metal detector and the deflecting mechanism (such as a guide baffle) are needed. The relatively long horizontal duct characterizing the prior ar constructions is disadvantageous where two consecutive fiber processing machines have to be arranged at a short distance from one another. It is a further disadvantage of the prior art constructions that a certain standard reaction time is present between the sensing of the foreign body and the switching of the guide baffle resulting, occasionally, in an excessive removal of fiber material together with the foreign body.